This invention relates to electrical power supply control circuitry and more particularly to a control for controlling a lamp or other electrical device using either the device""s ON/OFF switch or a remote wall switch which controls the energization of a conventional electrical outlet which supplies power to the device.
In household electrical systems, it is common to supply a wall outlet with electrical power through a wall switch positioned near an entryway. A lamp may then be plugged into the switched wall outlet. If the switch at the lamp is left on, the lamp can be turned on and off from the wall switch. This allows a person entering a dark room to turn on the lamp from the wall switch and avoids the need to search for the lamp switch in the dark.
Commonly, however, it is more convenient to turn the lamp off using the switch near the lamp. As a result, when the person leaves and later re-enters the room after dark, an attempt to turn on the lamp at the wall switch fails. Also, if the wall switch is turned off, the lamp cannot be turned on using the lamp switch. The bedside lamp illustrates the problem. While it is convenient to turn the lamp on using the wall switch when entering the room after dark, it is more convenient to use the switch near the lamp to turn the lamp off when retiring. As a result, in the morning when the room is well lit by daylight, the bedside lamp switch is typically left switched off. Thus, at nighttime when the room is reentered, the wall switch can""t be used to turn the lamp on again.
It would thus be desirable to provide a switching mechanism device that can be used to control a lamp that is plugged into a switched outlet from either the wall switch or the lamp switch.
For ease of installation and to limit expense, it would further be desirable to provide a field installable control device that can be used without requiring modification to the wall switch, the lamp, or the lamp switch, or alternatively to provide a new lamp fixture that can be used without modifying the wall switch or other parts of the existing wiring.
The present invention takes the form of methods and apparatus for controlling a lamp or other electrically operated device that is connected to receive electrical power from a conventional electrical wall outlet socket energized under the control of a manually actuated wall-mounted switch. The lamp or other device is controlled by a second manually actuated switch located at the electrically operated device. In accordance with the invention, an electrically controlled switch is connected between the wall outlet socket and electrically operated device and is controlled by the combination of a first control signal produced whenever the wall-mounted switch is actuated and a second control signal produced whenever the second switch is actuated. A control circuit actuates the electrically operated switch in response to both the first and the second control signals such that the electrically powered device can be independently controlled by actuating either the manually-actuated wall mounted switch or the second manually actuated switch located at said utilization device.
The first control signal may be generated by a voltage detector connected to the wall outlet to sense when the voltage delivered through the wall mounted switch changes. The second control signal may be produced by applying a low-level DC control voltage across the series combination of the device and the second switch, and then sensing the resulting current through the second switch when it""s ON.
In one embodiment of the invention, in which the electrically operated device is powered from the switched wall outlet terminals, an alarm device is actuated whenever either the manually operated wall switch or the second manually operated switch at the device is left in the OFF position.
The control circuit which actuates the electrically operated switch may be implemented with a state memory device having at least two states, the state memory device being connected to change state in response to either the first or the second control signal and to operate the electrically operated switch whenever it changes state.
The invention may advantageously take the form of a control adapter for connecting an electrical device to a standard electrical outlet that is connected to a source of electrical power through a wall-mounted switch having ON and OFF positions. A female socket mounted on the adapter housing receives the device""s standard male electrical power supply plug and a male adapter plug on the adapter housing plugs into the switched wall outlet. In one such arrangement, the power from the switched wall outlet is supplied to the connected electrical device under the control of the electrically operated switch. In an alternative arrangement, a second male plug on the housing connects to an unswitched socket on the wall outlet, and electrical power from the second plug is supplied to the connected device through the electrically operated switch.
In a further embodiment, an outlet adapter including male plugs for establishing electrical connections to a power source and for sensing the state of the wall switch is used with a device adapter which includes the second manually operated switch and connectors which permit the device adapter to be electrically connected between the wall adapter and the device.
These and other objects, features and advantages of the invention will be more clearly understood by considering the following detailed description of a preferred embodiment of the invention. In the course of this description, frequent reference will be made to the attached drawings.